That's just how the matchmaking is set up right now. It tries to balance the player's skill level between the teams. The best player will be on the team with the worst player, and it keeps shuffling the teams each match as people join and leave until the match is lopsided and everyone gets a message saying that it will be splitting up the teams to find a better match. That's just quickplay though. Competitive is based on your glory rank, and is designed to be more team oriented. So complain all you want about your rank being based on your team merits, that won't change.